@bmike: I think you completely replaced the original question with a question of your own making. I don't think the OP was asking "what (else) makes ML more security-conscious?". I think he was asking why they're doing what they're doing.
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iconoclastAug 3 '12 at 18:49

Precisely. We close questions that simply ask "Why did Apple do X" when they are primarily for gripes, discussion, and not seeking a question that is practically faced and realistically answered by people outside the company.
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bmike♦Aug 3 '12 at 19:05

If it's a bad question, close it. Don't change it to a completely different question -- that's disrespectful to the OP. If you want the new question asked, ask it yourself.
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ReidNov 21 '12 at 20:04

4 Answers
4

Apple computers have long been considered "virus free" although Apple stopped pushing this as a selling point earlier this year in the wake of several Apple targeted viruses.
The truth is that a virus can be programmed for mac much like a software application can, the reason for the lack if infections on mac was merely the same as the reason for lack of some apps in the past, the relative unpopularity vs windows machines meant it was less practical to program for mac.
With macs now being more popular than ever before, Apple now has to implement strict measures to hold on to their clean, virus free image, hence Gatekeeper being added to Mountain Lion.

The process which is checking for permission to run apps is called GateKeeper.

As per the following System Preferences screenshot, you are able to configure how it behaves. You can allow it to allow anything to run, only MAS apps to run, or a mixture of MAS apps, and known developers:

The idea for increased security is obviously because security is very very important. It's important for you, to know that you can trust the apps that you use, and it's important for Apple, to know that they can kill apps that they subsequently become aware are malicious or dangerous for users to run.

Once you accept an app to run, it's signature is added to an internal "whitelist" such that you only need to be asked once in order to allow an app to run. If you use the default setting (as per screenshot) you can still run any app by right clicking on it's icon and clicking open. This will require subsequent confirmation, but again once you have confirmed it once, you are good to go until such time as the apps signature changes (updates etc).

Apple computers come with an implicit as well as explicit contract that Apple employees will help users with software problems (time and location limited of course), so adding features that help users not need malware removal help is clearly in Apple's interest even if you don't subscribe to the view that OS X is designed with the user's best interests to prevent malware or other surprises from getting a chance to run.